Barnhart Island Bridge Fathometer Survey

Type: Hydrographic Services
Location: St. Lawrence County, NY
Date

Completed

Objectives

• Collected bathymetric data in the water from a 21’ survey vessel using R2Sonic 2022 multibeam sonar


• Collected bathymetric data onboard a remote-controlled Z-boat using R2Sonic 2020 multibeam sonar


• Conducted land-based surveying with Trimble S-5 total station and R-8 RTK GPS


• Integrated above- and below-water data into a unified elevation model


• Delivered results in compliance with NYSDOT “Technical Requirements of Fathometer Surveys” standards

The Barnhart Island Bridge spans the South Channel of the St. Lawrence River in Massena, New York, connecting Barnhart Island—part of Robert Moses State Park within the Thousand Islands region—to the mainland. Owned and maintained by NYPA, the bridge provides critical vehicle and pedestrian access to this environmentally and recreationally significant area.

To help ensure the bridge’s long-term integrity, Prudent Engineering was engaged as subconsultant to perform an underwater inspection and fathometer survey. Our team completed all work with a strong emphasis on field safety, carefully gathering elevation data—above and below the waterline—to support structural evaluation, maintenance planning, and the ongoing safe use of the bridge.